Correction device for gyroscopic compasses and the like



April 28, 1942. w. G. HARDING r-:TAL 2,281,286

CORRECTION DEVICE FOR GYROSGPIC COMPASSES AND THE LIKE Original Filed May 5, 1938 3 Sheets-Sheet 1 April 28, 1942. w. G. HAR'DING ETAL 2,281,286

CORRECTION DEVICE FOR GYROSCOPIC COMPASSES AND THE LIKE Original Filed May 5, 1938 sheets-shet 2 April 28, 1942. w. G. HARDING ETAL 2,231,285

CORRECTION DEVICE FOR GYROSCOPIC COMPASSES AND THE LIKE original Filed May 5, 1'938 s sheets-sheet 3.

AT'TORNEY Patented Apr. 28, i942 CORRECTION DEVICE FOR GYROSCOPC CORWASSES AND THE LIKE original application May 5, 193s, serial No. 206,208. Divided and this application October 19, 1939, Serial No. 300,182. In Great Britain May 7, 1937 7 Claims. (Cl. 33-126) lThis application is a division of our copending application, now Patent No. 2,273,808, dated February 17, 1942, for Systems for transmitting indications.

The present invention relates to transmission systems for transmitting indications from a measuring or indicating instrument, such as a magneticz or gyroscopic compass, and in particular to. means for introducing corrections into the transmission cansv so as to correct for error of known type 1n the instrument.

In accordance with the present invention we provide a system for controlling a controlled object so that the same moves non-proportionally (e. g. for introducing a systematic correction) to the movements of a controlling object or' instrument, wherein the controlled object is moved by a servo-motor turning proportionally therewith and controlled by means operated in part by the instrument or by a repeater reproducing the position of the instrument and .in part by a fol'-4 low-back from the servo-motor, the required degree of non-proportionality of the operation be-v Fig. 1 is a diagrammatic lay-out of a'system y in accordance with the present invention;

Fig. 2 shows another embodiment of the in vention;

Fig. 3 is a diagram of the circuit arrangements of part of the system of Fig. 1;

Fig. 4 illustrates a further embodiment of the' movements of the compass in that the controlled body is corrected for the aforesaid systematic errors of the compass. The non-proportionality results from the use of a corrector mechanism, and in accordance with the principles of the present invention, this mechanism is inserted in the follow-back from the servomotor to a controller operated from the gyra-compass.

Fig. 1 shows a systemsimilar to that described with reference to our aforesaid parent application, to which reference is directed, but wherein a servomotor 34 is employed, coupled to =a shaft 6 through gearing 35, 36, and wherein transmitter 2 is a Selsyn transmitter energized from an alternating current supply 3'. The receiver 5' is a receiver of the Selsyn type, but the single-phase winding on the stator, instead of being excited from the alternating current supply las in an ordinary Selsyn transmission, is connected to the amplifier 31 through the synchronizer38: said winding therefore acts as the secondary winding of a variable rotary transformer. Since this winding has induced in it an electrical signal proportional to its position relative to the three-phase winding, a Selsyn device used in this manner, is often referred to as a Selsyn signal generator." Connections are made to the'rotor of receiver 5 via slip rings 9, and to the stator via slip rings 39.

The amplifier 3l causes the servomotor 34 to run until the input to the amplifier 31 is zero. An amplifier suitable for this purpose is shown in U. S. application, Serial No. 148,670, iled June 17, 1937, for Position control systems, R. H. Nisbet, inventor.

Servomotor 34 will thus cause shaft 6 to rotate the rotor of receiver 5 relatively to the stator through the angle turned through by transmitter 2. A correction for errors of the compass is applied by a corrector-mechanism to rotate the stator of receiver 5. The corrector-mechanism shown is a variation of that described in Patent No. 2,128,559, to which reference may be made ed for example on the ships bulkhead, is moved I by a vservomotor to follow the indications transmitted from the compass, the following movement, however, being non-proportional with the for the theory of its operation. A more detailed explanation of the operation of the particular variation illustrated can also be found in the aforesaid parent application, with reference to- Fig. l of that application. It is suiiicient to remark here that cam I4 is an eccentric whose ecccntricity` is adjustable in accordance with the ships speed and latitude, and that, as the servomotor 34 rotates, this cam oscillates the lever I5 and applies the required corrections through the 34, and this controller is affected by the motor (the follow-back action) directly through the shaft 6, and indirectly to provide the correction through the correction mechanism and rack-bar I 9. The correction is thus introduced in the follow-back connection, the repeater 5' serving as a kind of electrical differential. It is also possible to apply the correction by means of -a mechanical differential 33, and such a system is shown in Fig. 2.4 In this arrangement, the stator of receivery 5' remains stationary, so that slip rings 39 are not required for making electrical connections to the stator winding. The systems of Figs. 1 and 2 operate generally in the same manner as does that described in relation to Fig. 1 of the ldrawings of the application aforementioned. 'I'he advantage of using the servomotor 34 is particularly apparent when Selsyn relay transmission is employed (i. e., when the transmitters 1 are "Selsyn transmitters transmitting to a large number of Selsyn receivers). In this case, the frictional and driving loads of the receivers become effective on the transmitters 1, and the torque required to turn these is greater than can be provided with accuracyby a receiver such as 5' alone.

In a practical form of the system of Fig. 1 the stator and rotor of the receiver 5' may be interchanged, that is to say; the servo motor 34 is geared to the stator, whereas the corrector lever I5 is geared to the rotor. In this way the load on the corrector is still further lightened, since it is easier to turn the rotor than the stator.

Moreover, the Worm gearing I0, II may be replaced by a train of spur gears, as may also be ing the output from the normal input from the variable transformer 5'. The next movement takes the contact arm 50 to contact stud 52 or 53 according to the direction of movement. These two studs are connected together, and to terminal 44 of the primary winding 45 of transformer 45. This winding 45is therefore short-circuited.

and` the output of the transformer 46 is conse 1 with terminals 54 and 55, which are connected to rack-and-pinion gearing 23, 24, and rack-andgear sector I8, I9. The member 2|] is in this case replaced by a gear turning about an axis parallel to the axis I1 of card I2. The servo motor 34, the receiver 5', and all the gears, therefore, have parallel axes and can be disposed around card I2.

Fig. 3 is a diagram of the circuit arrangementsl in one form of synchronizer for use at 33 in the system of Fig. 1. The input terminals receive the output from the receiver or variable transformer 5' of Fig. 1. This input is applied to the resistance 4I through resistances 42, 43. One side of resistance 4I is connected to terminal 44 of the primary winding of a transformer 45, the secondary winding 41 of this transformer being connected to the output terminals 49, which are connected to the amplifier 31 of Fig. 1. The other terminal 49 of the primary winding 45 is connected to a rotary contact arm 50, which is spring-constrained to a central position in which it makes contact with a contact stud 5I connected to resistance 4I. Under normal conditions, therefore, the primary winding 45 is connected across the resistance 4I, `so that the voltage developed across resistance 4I, which voltage is part of the input voltage from the variable transformer 5'. is applied to transformer 45 and therefore to the amplifier 31.

If, initially, the indication given by card I2 differs from that given by compass card I by more than half a revolution of the receiver 5', it becomes necessary to supersede this normal condition of operation by a manually controlled condition. For this purpose, a handle (not shown) is provided for turning the rotary contact arm 50 to one side or theother against the centralizing springs.

The first movement o f the arm 50 breaks the contact of the arm with stud 5I, thus disconnect- In Figs. 1 and 2 we have shown examples of relay transmission in which a servomotor is used to provide the necessary power to drive the transmitter (or transmitters) 1, andwe have employed therein the principle that the servomotor 34 is.

directly coupled to the transmitter 1 so as t0 turn proportionally therewith, the correction being inserted between the servomotor 34 and the controller for the servomotor (i. e., receiver 5') This,

feature is an important one, and it is embodied also in the forms of the invention `shown in Figs. 4 and 5.

In Fig. 4, the transmitter 2 geared to the compass I is of the "Selsyn type energized from alternating currenbmains as in Figs. 1 and 2. It transmits to a receiver 5', and a control voltage is obtained from the stator for' controlling the servomotor 34 through synchronizer 33 and amplifier 31, as before. servomotor 34 is directly geared to the corrected shaft 5' and to the relay transmitters, one of which is shown at 1.

servomotor 34 has a follow-back connection to the rotor of receiver 5', as explained herein, and the corrector mechanism is included in this follow-back, so that, although the repeater 5' turns proportionally to the uncorrected indication of compass l, shaft i turns proportionally to s. compass indication that is corrected. For this reason, there is secured to the shaft 6' the compass card I2 on which the true course may be read against the flxed index I3.

Means are provided for adjusting the position of a pin through a small langle relative to the card I2 around the axis of shaft 5. As shown, pin 55 is mounted in a lever 51, pivoted on shaft 6', the relative angular positions of card I2 and lever 51 being adiustable by a suitable adjusting worm screw 58, which is-carried in bearings in the boss 59 at the back of card I2. The screw 53 is turned by means of milled wheel 55 for altering the adjustment which is shown by a scale 5I and pointer 52. In this way the correction for compass fdamping error may be introduced.

The pin 55 engages in a radial slot in a secondary compass card I2' fixed to shaft 3 and coupled by gearing 53, 53 to the rotor of the re slidably mounted transversely in guides 55, 51.-

The position of carriage 55 in the guides is determined by screw 33, and is set by thumbscrew t9, being shown by the reading of anindex 1U against a scale of corrections 1I. The scale 1I may be set-out in terms of ships speed against latitude, or alternatively, in correction numbers, the correct setting then being ascertainable from tables.

By means of the adjustment of carriage 35 transversely of receiver 5', shaft 6 is displaced to an eccentric position relative to shaft B', whereby shaft 6 turns through an angle differing from that turned through by shaft 6' by an amount which will correct for the north-steaming error of the compass, provided that the eccentricity is suitably adjusted.

'Ihe arrangements for synchronizing the system of Fig. 4-are similar to those of Figs. 1 and 2, v

except that the uncorrected" card readings are read on card I2' against the index 23 fixed to the carriage 65.

In Fig. 5, a system is illustrated very similar to that of Fig. 4; it is distinguished by the fact that the controller for the servo motor 34 is not the receiver, but is a two-part controller, of which one part is moved with or by the card I2 and the other with or by the card I2'. As shown, the servo motor 34 is a direct current motor and the two-part controller is of the contact-making type.

The transmitter 2 geared to the compass I is lof the step-by-step type supplied from a direct current supply 2' and transmits to a receiver- 5, and turns the uncorrected" shaft 3 and card I2' through gearing 12, 13. The servo motor 34 turns the corrected shaft 6' and card I2 through gearing 35, 36. The axis of shaft 6 can be offset from the axis of shaft 6' by sliding the carriage 65 in the guides 66, 61, as in the system of Fig. 4, to provide a desired correction. Mounted on the shaft carrying card I2 is a disc 14 carrying contact segments 15, 16, which cooperate with contact rollers 11, 18 mounted on a bracket 13' secured to card I2'. 'I'he servo motor 34 is controlled by the relative angular position of the contact segments 15, 16, and rollers 11, 18. Many circuit arrangements are known which are suitable for this purpose. Preferably, servo motor 34 has a continuously energized field winding, the contact arrangement being such as to pass current in one direction or the other through the armature according Ato the direction of rotational displacement of card I2', relative to card I2, from their position of correspondence. As shown in Fig. 5, the direct current supply mains 19 are connected to the motor 34 to energize the field windings, and thence they are connected through current-limiting resistors, (not shown), to sliprings 83 on a shaft connected to card I2', and thence to the rollers 11, 13. The armature of motor 36 is connected to slip-rings 3| on a shaft coaxial with and connected to shaft 6' and card I2, and thence to the contact segments 15, 16. Segments 15, 16 are arranged in pairs, the segments of one pair being on one`side of disc 14 and being separated by a narrow radial slct, while segments of the other pair 16 are on the other side of disc 16 and are separated by a similar slot; the two slots are in the same axial plane. Diagonally opposite segments of the two pairs are connected to each other, so that the whole arrangement acts as a change-over switch in which the supply mains 13 are connected to the armature of motor 34 through resistances, with one polarity or the other according to the direction of departure of discs I2', I2 from'their position of correspondence. The motor 3 is therefore always caused torun so as to restore .the system to such position of correspondence and, in so doing, turns shaft through a different angle from that turned through by shaft G-,vthus introducing the desired correction.

A synchronizing handle 25 for initially setting the' system is provided for forcibly turning shaft 6, until card I2', as read against index 29, matches the reading of the compassv I.

In the systems of Figs. 1, 2, 4 and 5, and similar systems in which the servo motor 34 is directly coupled to the transmitter 1 and the corrector,

.or similar device for ensuring non-proportionality, is in the repeat-back from the servo motor to its controller it is important to prevent lost motion in the repeat back, otherwise any attempt to ensure high sensitivity, in order to obtain accuracy in working, will result in hunting of the system. For this reason we spring-load the whole corrector mechanism, and preferably also the gearing, so as to keep all the parts under tension in one direction.

In Fig.' 1 there is shown a spring 82, one end of which is attached to a fixed support 33, while the other is attached to a wire or tape passing round a sleeve 34 forming an extension of the stator of receiver 5'. The spring tension tends to rotate'the stator. It is lesseasy to spring-load the system of Fig. 2, since itis difl'lcult to avoid lost motion in the mechanicall vdifferential 33. In the system of Fig. `2, we employ a reversing gear between differential 33 and receiver 5' in order that shafts 6 and 6' shall turn in the same direction, and thus that the use of spring tension'constraint may be facilitated.

As shown in Fig. 6, the differential 33 of Fig. 2 adds the movements of the rack member 20'. and that of shaft 6' to produce rotation of the hollow shaft 86. This movement is led into the revers-l, i

ing gear 85. which is similar in construction "to the differential 33, but has its casing xedf The shaft 6 is continued through the hollow shaft 8.3,.

and is linked to shaft 6 by the coiled spring 31,

. which is biased to apply a torque in the same sense whatever be the lamount of correction introduced between shafts 3 and 6'.

As many changes could be made in the above scription or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we j declare that what we claim is:

1. A system for correcting for lthe North steaming'and other errors of.a gyro compass at a repeater compass comprising a' master compass, a

variable controller for Vretransmittingsignalsreceived from a transmittenat the master compass proportional to the'deviation thereof, a motor pass at a remote position from the master com-I pass, controlled from said relay transmitter, an error correction device actuated by said motor. dilerentially controlled means for adjusting said signal generator operable directly by said correction device and by said motor to obtain a corrective signal from said generator and thereby correct the directly actuated relay transmitter and the repeater compass controlled therefrom so that the repeater compass gives a directional indication free of error.

3. A system for correcting for North steaming A and other errors of a gyro compass at a repeater compass card comprising a master compass, a Variable controller for retransmitting signals received from a transmitter at the master compass proportional to the deviation thereof, a motor positioned by the signal transmitted by the controller, a repeater compass card rotated by said motor, an. error correction device actuated by said motor, dierentially controlled means for positioning said variable controller through ,said correction device and through direct operation of said motor to obtain a corrective signal from the controller for said motor and thereby directly correct the position of said repeater compass card so that the same gives a directional indication free of error.

4. A system in accordance with claim l in which the rotor of said controller and the rotor of said relay transmitterl are mounted on the same shaft.

5. A system in accordance with claim 3 in which said controller is an electric signal generator having a rotatably adjustable stator actuated by said correction devide and a rotor actuated by said motor.

6. A system in accordance with claim 3 in which said controller is an electric signal generator h'aving a rotor which is positioned by a mechanical differential, separate portions of which are respectively actuated by the correction device and by the motor.

7. A system in accordance with claim 1 in which the correction device is provided by locating the controller and motor so that their respective cooperating shafts are arranged in adjustable 'eccentric relationship.

Wm AM G.'HARDING. ROBERT H. NIsBET. 

